The principal objective of this study is to determine the effect of ethanol on the metabolism of neurosteroids in the central nervous system (CNS). Neurosteroids such as 5alpha-pregnane-3alpha-ol-20-one (THP or Allopregnanolone) and 5alpha-pregnane-3alpha,21-diol-20-one (THDOC) have been shown to modulate the GABA/benzodiazepine binding sites and to exert anxiolytic and hypnotic effects. Modulation of these neurosteroids in the CNS by ethanol may be one of the underlying mechanisms for stress- related situations in humans, a side effect often observed in alcoholics during withdrawal. As part of a continuing effort to establish a mass spectrometric technique which has adequate sensitivity to routinely measure trace levels of neurosteroids in cerebral spinal fluid (CSF), we explored other approaches using gas chromatography mass spectrometry (GC/MS) after derivatizing neurosteroids with an electron capturing moiety. In this mode, with the exceptions of progesterone and dihydroprogesterone, various neurosteroids were detected at 1 pg level. Characterization of the level of neuroactive steroids in rat brain and plasma as well as in monkey CSF is now in progress using this method.